通过对地球同步轨道上的GOES2和GOES3卫星的磁场数据进行分析，研究了近地夜侧磁层（约6.6RE处）中子暴活动的发展。子暴事件定义为在低纬度地面上观测到的单一启动。磁场配置从更像尾巴的状态转变为更像偶极子的状态，这种变化最初在与地面启动相关的局部经度区域开始，并向东西两侧扩展。即使在地面上广泛记录到低纬度正电流湾的同时启动，这一现象也依然存在。发现由场向电流启动引起的磁场变化与地面启动同步，并在磁场变化最大时达到峰值。这表明子暴与跨尾电流的中断及其向与极区电离层相连的场向电流的转换有关。同步轨道附近的跨尾电流及其中断对于产生同步轨道上的磁场配置变化至关重要。
Abstract
Magnetic field data from the geostationary satellites GOES 2 and GOES 3 are examined to study the development of substorm activity in the near-earth nightside magnetosphere (around a radial distance of 6.6 RE). Substorm events are those in which a well-defined single onset is seen at low latitude on the ground. The field configuration change from more taillike to more dipolelike starts initially in a longitudinally localized region in association with the ground onset, and it develops westward and eastward, even when the simultaneous onset of the low-latitude positive bay is recorded in a wide longitudinal region on the ground. It is also found that the variation caused by the field-aligned current starts at the ground onset and reaches a peak at the time of the field change. The present results are consistent with the view that the substorm is associated with a disruption and subsequent conversion of the cross-tail current to the field-aligned current connected with the polar ionosphere. It is indicated that the cross-tail current near synchronous orbit and its disruption are important in producing the field configuration change at synchronous orbit.
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